The present application claims priority to Europen application 00107817.9 filed on Apr. 12, 2000, the subject matter of which is hereby incorporated by reference.
The present invention is directed to dispersions, a process for preparing these dispersions and their use in the preparation of coating mixtures for inkjet media.
It is known that dispersions, for example water-based dispersions, can be prepared from pyrogenically prepared oxides. Aqueous dispersions can be used to prepare coating mixtures which are applied to paper or films. The coated films may then be printed using an inkjet printer. In this case, one objective is to obtain dispersions which are filled as highly as possible (high solids content) but with a low viscosity.
The invention provides dispersions which are characterised in that they consist of a liquid phase, preferably water, and a solid phase. The solid phase consists of a pyrogenic oxide, doped using an aerosol, the BET surface area of which is between 5 and 600 m2/g. The pyrogenic oxide preferably comprises silica prepared by the method of flame hydrolysis or flame oxidation and which has been doped with one or more doping component(s). Preferably the doping component is an aluminium oxide, and doping is accomplished by the method of aerosol application, in which the amount of doped material is between 1 and 200,000 ppm and the doping component(s) are applied via a salt or a salt mixture. The solid phase in the dispersion should be present in a proportion by weight between 0.001 and 80 wt. %.
The invention also provides a process for preparing chemical dispersions in which a pyrogenic oxide, doped using an aerosol, is introduced into a liquid, preferably water, in a proportion by weight of between 0.001 and 80 wt. %. This dispersion is then subjected to a milling step, which may be performed using a ball mill, a pearl mill, a high-pressure mill, or any other known mill, preferably using a dispersing system in accordance with the rotor-stator principle (Ultra-Turrax(trademark)).
The invention also provides for the use of dispersions in preparing coating mixtures (particularly for inkjet papers, inkjet films or other inkjet materials), as a ceramic raw material, in the electrical industry, as a polishing agent (CMP applications), in the cosmetics industry, in the silicone and rubber industry, to adjust the rheology of liquid systems, as a starting material for preparing glass or glass coatings or melting crucibles, in dentistry, in the pharmaceutical industry, in PET film applications, as a starting material for preparing filter ceramics or filters, as a rust prevention agent, in inks and in battery separators.
One advantage of using highly filled, i.e., dense, and low viscosity dispersions such as those described herein in paper production (i.e., in the preparation of mixtures for coating papers and other media) is that proportionately less water has to be evaporated in the drying step after applying the dispersion (coating mixture). This provides a saving in energy.